A federal district court has ruled that the National Labor Relations Act cannot be applied to teachers in church-related schools because it would interfere with religious freedom.

The decision, handed down here by Judge Donald W. VanArtsdalen, upholds a major argument of pastors of the Roman Catholic Archdiocese of Philadelphia, which has opposed involvement of the National Labor Relations Board in union efforts of some 2,300 lay teachers.

Results of a union election held in the archdiocese June 14 will continue to be secret, pending the outcome of a separate legal case.

Judge VanArtsdalen issued a preliminary injunction against the election in February, and an NLRB appeal of that action was denied in March by a Circuit Court of Appeals.

U.S. Supreme Court Justice William J. Brennan Jr. decided in May that the election could be held but that the results were to be impounded pending a final ruling by the U.S. Circuit Court of Appeals. Oral arguments on the original injunction will be heard by the appeals court Sept. 8.

William Ball, a Harrisburg attorney who represented the Philadelphia archdiocesan pastors who opposed the election, called Judge VanArstalen's ruling "an excellent decision from the point of view of religious liberty, over-regulation by government of voluntary efforts, and legal scholarship."

He said if the National Labor Relations Act had been intended to apply to church-related schools, it would have made the government "the arbiter of everything that takes place within a religious school," including the cirriculum.

Ball noted that the ruling specifically related to the issue of government involvement in union matters in church-related schools, but that it did not address the question of whether teachers in such schools should be permitted to have unions. He pointed out that there are such unions in several Roman Catholic dioceses.